Field Investigations on the Interrelationships of the Big-Headed Ant, the Gray Pineapple Mealybug, and Pineapple Mealybug Wilt Disease in Hawaii

The population density of the big-headed ant was higher during the second (ratoon) crop than during the first crop of pineapple at both Poamoho and Molokai. At Poamoho, no mealybug wilt plants were found in plots where ants had been controlled, while the number of such plants increased sharply during the second crop in plots where ants were not controlled. The incidence of mealybug wilt was higher at the edges of plots than toward the middle reflecting the greater abundance of ants and mealybugs on the margins on the plots. Wilt spread in a contagious manner with the number of diseased plants increasing at a logrithmic rate over time. The coefficient of correlation between the number of ants caught in pitfall traps and the percentage of mealybug infested plants was very high (r = 0.97). Infestation of the Molokai experimental planting by big-headed ants started at the edges of plantings adjacent to abandoned fields and waste areas. Invasion progressed slowly, and two and one half years elapsed before all plots had become infested. Ant and mealybug populations in infested plots increased gradually and appeared to be strongly influenced by the phenology of the pineapple plants during the first fruit crop. Unusually heavy rainfall during March and April 1979 may have caused the dramatic reduction in ant populations observed then. Highest ant population levels occured about three years after planting when all untreated plots became nearly uniformly infested. Pest management strategies for pineapple ants and mealybugs are discussed, and it is suggested that a program of ant surveillance using bait stakes, coupled with treatment of field margins and adjacent infested old fields or uncultivated areas when ants are discovered, can prevent migration of these pests into plantation fields

Deterministic and Stochastic Spin Diffusion in Classical Heisenberg Magnets

This computer simulation study provides further evidence that spin diffusion in the one‐dimensional classical Heisenberg model at T=∞ is anomalous: 〈S j ( t )⋅S j 〉 ∼t −α 1 withα1 ≳1/2. However, the exponential instability of the numerically integrated phase‐space trajectories transforms the deterministic transport of spin fluctuations into a computationally generated stochastic process in which the global conservation laws are still satisfied to high precision. This may cause a crossover in 〈S j ( t )⋅S j 〉 from anomalous spin diffusion (α1 ≳ 1/2) to normal spin diffusion (α1 = 1/2) at some characteristic time lag that depends on the precision of the numerical integration

Spin Diffusion in Classical Heisenberg Magnets with Uniform, Alternating, and Random Exchange

We have carried out an extensive simulation study for the spin autocorrelation function at T=∞ of the one‐dimensional classical Heisenberg model with four different types of isotropic bilinear nearest‐neighbor coupling: uniform exchange, alternating exchange, and two kinds of random exchange. For the long‐time tails of all but one case, the simulation data seem incompatible with the simple ∼t −1/2 leading term predicted by spin diffusion phenomenology

A Simulation Study of the Factors Influencing the Risk of Intraoperative Slipping

AbstractBackgroundTo identify the impact of weight, table surface, and table type on slipping in a simulation of minimally invasive gynecologic surgery.MethodsA mannequin was placed into increasing Trendelenburg until a slip was observed; the table angle at the time of the event was measured (slip angle). The influence of mannequin position (supine vs. lithotomy), weight, table surface, and model was evaluated. A linear regression model was used to analyze the data.ResultsMannequin weight, bed surface, and bed type all significantly impacted the slip angles. In general, higher mannequin weights tolerated significantly more Trendelenburg before slipping in the supine position but less in lithotomy compared to lower weights. In lithotomy, the disposable sheet and gelpad performed worse than the bean bag, egg crate foam, and bedsheet. There was no difference in slipping because of bed surface in the supine model. The Skytron operating table performed significantly better than the Steris operating table when tested with the bedsheet.ConclusionOperative position, patient weight, and bed surface together influence the slipping propensity. In lithotomy, heavier patients were more prone to slipping while the inverse was true in supine. The egg crate foam, bean bag, and bedsheet were the best antislip surfaces. Operating room table choice can mitigate slippage

High-resolution isotopic evidence of specialised cattle herding in the European Neolithic.

Peer reviewe

Reconstruction of a first-order phase transition from computer simulations of individual phases and subphases

We present a new method for investigating first-order phase transitions using Monte Carlo simulations. It relies on the multiple-histogram method and uses solely histograms of individual phases. In addition, we extend the method to include histograms of subphases. The free energy difference between phases, necessary for attributing the correct statistical weights to the histograms, is determined by a detour in control parameter space via auxiliary systems with short relaxation times. We apply this method to a recently introduced model for structure formation in polypeptides for which other methods fail.Comment: 13 pages in preprint mode, REVTeX, 2 Figures available from the authors ([email protected], [email protected]

Spin dynamics simulations of the magnetic dynamics of RbMnF3_3 and direct comparison with experiment

Spin-dynamics techniques have been used to perform large-scale simulations of the dynamic behavior of the classical Heisenberg antiferromagnet in simple cubic lattices with linear sizes $L\leq 60$. This system is widely recognized as an appropriate model for the magnetic properties of RbMnF$_3$. Time-evolutions of spin configurations were determined numerically from coupled equations of motion for individual spins using a new algorithm implemented by Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions of exponential operators. The dynamic structure factor was calculated from the space- and time-displaced spin-spin correlation function. The crossover from hydrodynamic to critical behavior of the dispersion curve and spin-wave half-width was studied as the temperature was increased towards the critical temperature. The dynamic critical exponent was estimated to be $z=(1.43\pm 0.03)$, which is slightly lower than the dynamic scaling prediction, but in good agreement with a recent experimental value. Direct, quantitative comparisons of both the dispersion curve and the lineshapes obtained from our simulations with very recent experimental results for RbMnF$_3$ are presented.Comment: 30 pages, RevTex, 9 figures, to appear in PR

How does a cadaver model work for testing ultrasound diagnostic capability for rheumatic-like tendon damage?

To establish whether a cadaver model can serve as an effective surrogate for the detection of tendon damage characteristic of rheumatoid arthritis (RA). In addition, we evaluated intraobserver and interobserver agreement in the grading of RA-like tendon tears shown by US, as well as the concordance between the US findings and the surgically induced lesions in the cadaver model. RA-like tendon damage was surgically induced in the tibialis anterior tendon (TAT) and tibialis posterior tendon (TPT) of ten ankle/foot fresh-frozen cadaveric specimens. Of the 20 tendons examined, six were randomly assigned a surgically induced partial tear; six a complete tear; and eight left undamaged. Three rheumatologists, experts in musculoskeletal US, assessed from 1 to 5 the quality of US imaging of the cadaveric models on a Likert scale. Tendons were then categorized as having either no damage, (0); partial tear, (1); or complete tear (2). All 20 tendons were blindly and independently evaluated twice, over two rounds, by each of the three observers. Overall, technical performance was satisfactory for all items in the two rounds (all values over 2.9 in a Likert scale 1-5). Intraobserver and interobserver agreement for US grading of tendon damage was good (mean κ values 0.62 and 0.71, respectively), with greater reliability found in the TAT than the TPT. Concordance between US findings and experimental tendon lesions was acceptable (70-100 %), again greater for the TAT than for the TPT. A cadaver model with surgically created tendon damage can be useful in evaluating US metric properties of RA tendon lesions